Arduino UNO Q - Button - Debounce
When programming Arduino UNO Q to detect a button press, a single press might be detected multiple times. This happens because mechanical contacts rapidly bounce between LOW and HIGH — a phenomenon called chattering. This tutorial shows you how to fix it through debouncing.
Hardware Preparation
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Wiring Diagram
This image is created using Fritzing. Click to enlarge image
MCU Code — Without Debounce (for comparison)
The Arduino UNO Q has two processors: the STM32 MCU (handles real-time hardware control) and the Qualcomm MPU (runs Debian Linux). In this section, only the STM32 MCU is programmed — the Linux side stays idle. A later section will show how both processors work together.
This is the version without debounce from the Button tutorial. Notice how a single press may register multiple events:
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-button-debounce
*/
#define BUTTON_PIN 7 // The Arduino UNO Q pin connected to the button
int button_state;
int prev_button_state = HIGH; // HIGH = not pressed (pull-up)
void setup() {
// initialize the pushbutton pin as a pull-up input
pinMode(BUTTON_PIN, INPUT_PULLUP);
}
void loop() {
// read the state of the button (LOW = pressed, HIGH = not pressed)
button_state = digitalRead(BUTTON_PIN);
if (prev_button_state == HIGH && button_state == LOW) {
// button was just pressed (HIGH → LOW transition)
// TO DO: add your press action here
} else if (prev_button_state == LOW && button_state == HIGH) {
// button was just released (LOW → HIGH transition)
// TO DO: add your release action here
}
// save the last state
prev_button_state = button_state;
}
Detailed Instructions
- First time with Arduino UNO Q? Follow the Getting Started with Arduino UNO Q tutorial to get your development environment ready before proceeding.
- Wire the button: Connect one button pin to GND and the other to pin 7 according to the wiring diagram.
- Connect: Plug the Arduino UNO Q into your computer with a USB-C cable.
- Open Arduino App Lab: Launch Arduino App Lab and wait until it detects your Arduino UNO Q.
- Create a new App: Click the Create New App button.
- Give the App a name, for example: DIYables_ButtonDebounce
- Click Create to confirm.
- You will see a set of folders and files generated inside your new App.
- Find the sketch/sketch.ino file — this is where you will paste the MCU sketch.
Paste the sketch: Copy the no-debounce code above and paste it into the sketch file. Keep other files as default.
Upload: Click the Run button in Arduino App Lab to compile and upload to the STM32.
- Press the button once then release it — observe that multiple events may be logged (visible via the Bridge Monitor in the next section).
- Notice: This is the chattering effect — the next section fixes it.
MCU Code — With Debounce (using millis)
This version uses millis() to wait for the signal to stabilize before treating it as a real event. Only state changes that persist for more than DEBOUNCE_TIME milliseconds are accepted:
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-button-debounce
*/
#define BUTTON_PIN 7 // The Arduino UNO Q pin connected to the button
#define DEBOUNCE_TIME 50 // The debounce time in milliseconds; increase if output flickers
int last_steady_state = LOW; // the previous stable state from the input pin
int last_flickerable_state = LOW; // the previous flickerable state from the input pin
int current_state; // the current reading from the input pin
unsigned long last_debounce_time = 0; // the last time the state changed
void setup() {
// initialize the pushbutton pin as a pull-up input
pinMode(BUTTON_PIN, INPUT_PULLUP);
}
void loop() {
// read the current state of the button
current_state = digitalRead(BUTTON_PIN);
// if the state changed (due to noise or a press/release), reset the debounce timer
if (current_state != last_flickerable_state) {
last_debounce_time = millis();
last_flickerable_state = current_state;
}
if ((millis() - last_debounce_time) > DEBOUNCE_TIME) {
// the state has been stable for DEBOUNCE_TIME ms — treat it as real
if (last_steady_state == HIGH && current_state == LOW) {
// TO DO: button pressed action here
} else if (last_steady_state == LOW && current_state == HIGH) {
// TO DO: button released action here
}
last_steady_state = current_state;
}
}
- How it works: If the button state changes rapidly (bouncing), the timer resets each time. Only when the state is stable for 50ms is it treated as a real press or release.
- Pro Tip: If your button still shows multiple events, try increasing DEBOUNCE_TIME to 75 or 100.
※ NOTE THAT:
The optimal DEBOUNCE_TIME depends on the button quality and the application. 50ms is a safe default for most push buttons.
Simpler Debounce with the ezButton Library
For beginners and multi-button projects, we built the ezButton library — it handles INPUT_PULLUP, debounce, and edge detection automatically.
Single button with ezButton:
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-button-debounce
*/
#include <ezButton.h>
ezButton button(7); // create ezButton object attached to pin 7
void setup() {
button.setDebounceTime(50); // set debounce time to 50 milliseconds
}
void loop() {
button.loop(); // MUST call the loop() function first
if (button.isPressed()) {
// TO DO: button pressed action here
}
if (button.isReleased()) {
// TO DO: button released action here
}
}
- Install the library: Click the Add sketch library button (the open book icon with a + sign) in the left sidebar.
- Search for ezButton created by ArduinoGetStarted.com and click the Install button.
Bricks
No bricks added...
Sketch Libraries
No sketch libra...
Files
python
sketch
.gitignore
README.md
app.yaml
sketch.ino
- Search for Arduino_RouterBridge created by Arduino and click the Install button.
Bricks
No bricks added...
Sketch Libraries
No sketch libra...
Files
python
sketch
.gitignore
README.md
app.yaml
sketch.ino
- How it works: button.loop() must be called every loop cycle. Then button.isPressed() returns true exactly once per physical press, and button.isReleased() returns true exactly once per release — no chattering.
Multiple buttons with ezButton (three buttons on pins 6, 7, 8):
This image is created using Fritzing. Click to enlarge image
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-button-debounce
*/
#include <ezButton.h>
ezButton button_1(6); // ezButton object on pin 6
ezButton button_2(7); // ezButton object on pin 7
ezButton button_3(8); // ezButton object on pin 8
void setup() {
button_1.setDebounceTime(50);
button_2.setDebounceTime(50);
button_3.setDebounceTime(50);
}
void loop() {
button_1.loop();
button_2.loop();
button_3.loop();
if (button_1.isPressed()) { /* button 1 pressed action */ }
if (button_1.isReleased()) { /* button 1 released action */ }
if (button_2.isPressed()) { /* button 2 pressed action */ }
if (button_2.isReleased()) { /* button 2 released action */ }
if (button_3.isPressed()) { /* button 3 pressed action */ }
if (button_3.isReleased()) { /* button 3 released action */ }
}
Linux + MCU Bridge Programming
The Arduino UNO Q has two processors that work together: the MPU (Qualcomm, runs Debian Linux) and the MCU (STM32, runs Zephyr OS with your Arduino sketch). They communicate using RPC via the Arduino_RouterBridge library — never via raw serial ports.
- The button is connected to the MCU (STM32) — wired to a digital input pin on the STM32. The MCU reads and debounces button presses using the ezButton library.
- The MPU cannot read the button directly — it must request data from the MCU via Bridge.call(). The MCU responds with the press count or resets it.
- The MPU has Wi-Fi — because the MPU runs full Debian Linux with Wi-Fi, it can report press counts via Telegram and accept reset commands remotely.
- Communication: Bridge.call() on the Linux side invokes Bridge.provide() functions on the MCU side
- ⚠️ Reserved: /dev/ttyHS1 (Linux) and Serial1 (MCU) are used by the Arduino Router — never open them directly
In short: MCU debounces button presses and counts them → MPU requests the count → MPU forwards it via Telegram.
MCU sketch — button debounce with press counter and Bridge:
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-button-debounce
*/
#include "Arduino_RouterBridge.h"
#include <ezButton.h>
ezButton button(7);
int press_count = 0;
void get_press_count() {
Monitor.println("Press count: " + String(press_count));
}
void reset_count() {
press_count = 0;
Monitor.println("Press count reset to 0");
}
void setup() {
button.setDebounceTime(50);
Bridge.begin();
Monitor.begin();
Bridge.provide("get_press_count", get_press_count);
Bridge.provide("reset_count", reset_count);
Monitor.println("Button Debounce Bridge ready");
}
void loop() {
button.loop();
if (button.isPressed()) {
press_count++;
Monitor.println("Button PRESSED — count: " + String(press_count));
}
if (button.isReleased())
Monitor.println("Button RELEASED");
}
Python script (Arduino App Lab) — poll press count from Linux:
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-button-debounce
*/
from arduino.app_utils import *
import time
def loop():
while True:
count = Bridge.call("get_press_count")
print(f"Current press count: {count}")
time.sleep(3)
App.run(user_loop=loop)
- Note: Make sure Bridge.begin() is called in the MCU sketch and the sketch is uploaded before running the Python script on the Linux side.
- ⚠️ Warning: Never directly open /dev/ttyHS1 (on Linux) or use Serial1 (on MCU) in your code — these are reserved by the Arduino Router and accessing them will break the Bridge.
Detailed Instructions
- Upload the MCU sketch: Open Arduino App Lab, create a new App, paste the Bridge MCU sketch above into sketch/sketch.ino, install the ezButton and Arduino_RouterBridge libraries, and click Run.
- Add the Python script: Paste the Python code above into the Python tab of the same App.
- Run the App: Click Run — the Python side polls the press count every 3 seconds.
- Press the button several times.
- Check the console: Open the Console tab → MCU Monitor subtab to see press/release events. Open the Python Console subtab to see the polled count.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
Button Debounce Bridge ready
Button PRESSED — count: 1
Button RELEASED
Button PRESSED — count: 2
Button RELEASED
Button PRESSED — count: 3
Button RELEASED
Telegram Integration
You can query the button press count or reset it from anywhere via Telegram.
If you do not have a Telegram bot yet, see How to Create a Telegram Bot to get your bot token before continuing.
MCU sketch: Keep the same MCU sketch from the previous Bridge section — no changes needed. Make sure it is already uploaded and running on the STM32 before proceeding.
Python script (Arduino App Lab) — Telegram bot for button press tracking:
/*
* This Arduino UNO Q code was developed by newbiely.com
*
* This Arduino UNO Q code is made available for public use without any restriction
*
* For comprehensive instructions and wiring diagrams, please visit:
* https://newbiely.com/tutorials/arduino-uno-q/arduino-uno-q-button-debounce
*/
from arduino.app_utils import *
import requests
import time
BOT_TOKEN = "YOUR_BOT_TOKEN"
API_URL = f"https://api.telegram.org/bot{BOT_TOKEN}"
last_update_id = 0
def send_message(chat_id, text):
requests.post(f"{API_URL}/sendMessage", json={"chat_id": chat_id, "text": text})
def get_updates():
global last_update_id
resp = requests.get(f"{API_URL}/getUpdates", params={"offset": last_update_id + 1, "timeout": 5})
return resp.json().get("result", [])
def loop():
global last_update_id
updates = get_updates()
for update in updates:
last_update_id = update["update_id"]
msg = update.get("message", {})
chat_id = msg.get("chat", {}).get("id")
text = msg.get("text", "").strip()
if text == "/count":
count = Bridge.call("get_press_count")
send_message(chat_id, f"Button pressed {count} time(s) since last reset")
elif text == "/reset":
Bridge.call("reset_count")
send_message(chat_id, "Press count reset to 0")
else:
send_message(chat_id, "Commands:\n/count — get button press count\n/reset — reset the count to 0")
time.sleep(1)
App.run(user_loop=loop)
- Note: Replace YOUR_BOT_TOKEN with the token obtained from @BotFather on Telegram.
- Send /count to see how many times the button has been pressed since power-on or last reset.
- Send /reset to reset the counter to 0.
Detailed Instructions
- Upload the MCU sketch: Use the Bridge MCU sketch from the previous section (upload it first if not already done).
- Paste the Telegram script: Copy the Python code above into the Python tab of your App in Arduino App Lab.
- Set your token: Replace YOUR_BOT_TOKEN in the script with your actual bot token.
- Run the App: Click Run — the bot starts listening for Telegram messages immediately.
- Test it: Press the button 5 times, then send /count on Telegram — you should receive 5. Then send /reset and /count again to confirm it resets.
- Pro Tip: Use this as an event counter for counting visitors, machine cycles, or triggered alerts.
App Lab Console Output
sketch.ino
1#include "Arduino_RouterBridge.h"
Serial Monitor
Python
[2026-04-29 12:00:01] Telegram: /count
[2026-04-29 12:00:01] Button pressed 5 time(s) since last reset
[2026-04-29 12:01:30] Telegram: /reset
[2026-04-29 12:01:30] Press count reset to 0
[2026-04-29 12:01:45] Telegram: /count
[2026-04-29 12:01:45] Button pressed 0 time(s) since last reset
Telegram
12:45
Welcome to Telegram!
ArduinoBot
10:19
Chatting with Arduino...
BotFather
Yesterday
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OpenClaw Integration
OpenClaw integration for Arduino UNO Q button debounce is coming soon.
- Coming Soon: OpenClaw support for button press tracking on Arduino UNO Q will be covered in a future update.
Application/Project Ideas
- Visitor counter: Place a button at a door — press count tracks how many people entered
- Machine cycle counter: Count actuator cycles in a production line, check count via Telegram
- Manual event log: Press button to log a timestamped event on the Linux side (MPU has real clock)
- Multi-mode controller: Each button press cycles to the next mode; check mode via Telegram
- Press-to-order: Press button to send a Telegram "reorder" message for supplies
Challenge Yourself
- Easy: Modify the Bridge sketch to also track how many times the button was released
- Medium: Add a get_last_press_time() Bridge function that returns the number of seconds since the last press
- Advanced: Build a Telegram bot that automatically sends a message when the press count reaches a target number (e.g., "10 presses reached!")